In this April 23, 2018, photo, people wait in line outside the Supreme Court in Washington, to be in the gallery when the court hears arguments in on April 25, over President Donald Trump's ban on travelers from several mostly Muslim countries.
"Congress has granted the president sweeping power to suspend or restrict entry of aliens overseas", U.S. Solicitor General Noel Francisco said in court papers.
At Wednesday's argument, those challenging the ban are being represented by lawyer Neal Katyal, who has argued landmark cases in the Supreme Court both for and against executive power in the context of national security.
Francisco turned again and again to that process - explaining that the travel limitations are an attempt to apply diplomatic pressure to nations that the federal government has concluded do not provide sufficient information to vet travelers from those countries.
There are, in fact, 51 majority-Muslim countries, and the government maintains that the travel ban is targeting only those that are points of vulnerability, either because they lack the ability to verify the identity and background of those seeking to enter the USA or they have not cooperated with the US government or are "safe havens of terrorism".
September 24: Trump issues his third version of the ban following what the administration says was a deep dive into worldwide vetting procedures.
Kyle Shideler, director of the threat assessment office at the Washington-based Center for Security Policy, said he is not sure how the court might come down on the issue.
The current ban initially restricted travel from eight nations - Iran, Libya, Syria, Yemen, Somalia, Chad, Venezuela and North Korea - six of which were predominantly Muslim.
Other Justices pressed the Solicitor General on the question, asking if campaign statements count if the candidate in question is already holding elected office, such as a small-town mayor running for Congress.
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In the first half of the argument, Kennedy did signal that courts should be able to review words from candidates from the campaign trail.
The justices voted in December to allow the policy to take full effect pending their full consideration. It also affects two non-Muslim countries, blocking travelers from North Korea and some Venezuelan government officials and their families.
But before he can make that case, he will have to deal with the government's first argument - that foreign nationals outside the US have no constitutional rights, no right to litigate in USA courts and that the courts have no power to review the president's ban.
About 150 people demonstrated against the travel ban outside the courthouse on a rainy morning in the USA capital. Those restrictions were not challenged in court. Seema Sked, 39, stood before the court's plaza with a homemade sign that read, "Proud American Muslim".
The notion that the policy is nothing more than a dressed-up Muslim ban, Shideler said is "nonsensical". "It hurts me because it is singling out and demeaning Muslims due to their faith". Many expect the issue will eventually end up before the Supreme Court.
The immigration statute is enough for the court to strike down the ban, he said. The last time the court did that was the gay marriage arguments in 2015.
In return, USA attorneys will argue the president has constitutional authority on immigration and if the executive order violates immigration law.
People have been waiting in line for a seat for days. They also argue that his policy amounts to the Muslim ban that he called for as a candidate, violating the Constitution's prohibition against religious bias.
A decision in Trump v. Hawaii, 17-965, is expected by late June.